Influence of metal ions on the ⁶⁸Ga-labeling of DOTATATE.

The influence of metal cations (Fe³⁺, Fe²⁺, In³⁺, Cu²⁺, Ca²⁺, Al³⁺, Co²⁺, Lu³⁺, Ni²⁺, Pb²⁺, Ti⁴⁺, Y³⁺, Yb³⁺, Zn²⁺, and Zr⁴⁺) on the radiolabeling yield of [⁶⁸Ga(DOTATATE)] was evaluated. Our most important observation was that, within our experimental limit, the metal ion/ligand ratio plays a critical role on the influence of most metal ions. More in-depth studies, with Cu²⁺ and Fe³⁺, revealed that reaction temperature and concentration changes have little effect, but speciation changes with pH are crucial. Furthermore, we found that [⁶⁸Ga(DOTATATE)] is stable in the presence of high concentrations of Fe³⁺, Zn²⁺ and Pb²⁺, but transmetalates with Cu²⁺ at 95°C. Crown